This invention relates to a variable capacity compressor which varies the compression starting timing to thereby control the delivery quantity or capacity thereof, and more particularly to a compressor of this kind which has a sufficiently wide variable range of the delivery quantity or capacity.
As a conventional variable capacity vane compressor of this kind, a vane compressor has been proposed by U.S. Pat. No. 4,813,854 assigned to the present assignee, in which the compression starting timing is different between two compression spaces defined within the cylinder, that is, the compression stroke in one compression space commences at a retarded timing, as compared with that in the other compression space, thereby reducing the minimum delivery quantity or capacity of the one compression space and hence providing a wide variable range of delivery quantity or capacity of the compressor, while obtaining a sufficiently high level of discharge pressure during partial capacity operation of the compressor.
The proposed compressor has a control element having two cut-out portions formed in an outer peripheral edge thereof at almost diametrically opposite locations, except that one cut-out portion has one forward end edge with respect to the rotation of the rotor, which is located asymmetrically with an forward end edge of the other cut-out portion such that the compression starting timing in the one compression space is retarded as compared with that in the other compression space. The position of the one forward end edge of each cut-out portion determines the compression starting timing in the corresponding compression space. Therefore, when the compressor is in a full capacity operation, as well as in partial capacity operation, the compression starting timing in the one compression space is retarded as compared with that in the other compression space, thereby resulting in reduced delivery quantity or capacity in the one compression space and hence reduced total maximum delivery quantity or capacity of the compressor during full capacity operation.
Further, in the proposed compressor, the control element is controlled by control pressure created from high pressure or discharge pressure supplied from either one of the compression spaces. If the high pressure for creating the control pressure is supplied from the one compression space, whose delivery quantity or capacity is smaller than that of the other compression space at partial capacity operation of the compressor, when the compressor is started where the control element is in the partial capacity position so that the compression starting timing in the one compression space is retarded as compared with the other compression space, the control pressure does not promptly increase to a high level sufficient to cause rotation of the control element toward increased delivery quantity or capacity of the compressor at the start thereof, thus resulting in poor startability of the compressor.